Antenna impedance of a user equipment is easily affected by an external environment. For example, when a user holds a user equipment in the user's hand, or places the user equipment near the head of the user, or places the user equipment into a pocket, all such common actions may cause a significant change in the antenna impedance. For a radio frequency transceiver system, when an impedance mismatch occurs on an antenna port, communication performance deteriorates. For example, efficiency of a power amplifier is reduced, causing a decrease in transmit power and an increase in overall power consumption, and a noise coefficient of a receiver deteriorates, causing a decrease in sensitivity. In addition, with deployment of an LTE system, a user equipment needs to support an increasingly wide frequency range, and it is difficult to improve efficiency of a broadband antenna without increasing an antenna size of a handset, thereby causing a decrease in the communication performance.
An antenna impedance matching (Antenna Impedance Matching) apparatus, for example, an antenna tuner (Antenna Tuner), is a component used for tuning antenna impedance and is disposed at a feedback port of an antenna. On the one hand, the antenna tuner can reduce an impact of a change in the antenna impedance on performance of a radio frequency transceiver, increase airtime of the handset, and improve communication quality. On the other hand, for a broadband antenna, the antenna tuner can further tune the antenna impedance to improve efficiency of the antenna in an operating frequency band, thereby improving the communication quality.
In an existing solution, the antenna tuner may be implemented by combining multiple adjustable capacitor chips and fixed inductors outside the chips, where each adjustable capacitor chip may switch between different capacitance values by using multiple fixed capacitors and multiple switches. The antenna tuner may be implemented by using multiple adjustable capacitor chips in combination with multiple surface-mount inductor/capacitor components outside the chips. However, the antenna tuner is tunable within a narrowband frequency range, and can perform optimization only on a specific frequency band, and therefore, cannot flexibly tune impedance matching of an antenna according to a requirement.
In an antenna tuner that uses multiple semiconductor chips that have independent adjustable capacitors, an impedance matching network of the antenna tuner has a fixed structure after adjusting is completed. For different user equipments, a new antenna tuner needs to be redesigned and adjusted according to antenna characteristics of the user equipments, so that a development cycle is extended. In addition, because the antenna tuner needs to be implemented by using multiple semiconductor chips that have independent adjustable capacitors, a cost is high, and a large PCB area is occupied.
The antenna tuner may be formed by integrating multiple semiconductor chips that have independent adjustable capacitors into one semiconductor chip that has multiple adjustable capacitors, so as to reduce the cost and decrease the PCB area. However, such a structure of the impedance matching network is still fixed. For different user equipments, external components of the semiconductor chips of the antenna tuner still need to be redesigned and adjusted according to the antenna characteristics, so that a development cycle is extended. In addition, the fixed structure of the impedance matching network causes a limited frequency tuning range. To cover a broadband frequency range, external fixed capacitor/inductor components of the semiconductor chips must be replaced, and therefore, such an antenna tuner cannot meet requirements of a full-frequency band broadband system.
Moreover, the semiconductor chip with adjustable capacitors and the external capacitor/inductor components may further be encapsulated into one component, thereby decreasing the PCB area and reducing the cost. However, a topology of the impedance matching network and inductance values of the inductor components are fixed, and therefore, such a component is only used for a specific handset platform or a usage frequency band, but cannot be used as a general component. In addition, only a narrowband frequency range can be covered, and the requirements of the full-frequency band broadband system cannot be met.
Because a fixed topology network can obtain optimal performance only with adjusting and optimization according to the antenna characteristics, and an inductance value of an off-chip inductor or capacitor component is fixed and non-adjustable, the frequency range of the foregoing impedance matching network cannot meet the requirements of the full-frequency band broadband system.